Step 4B – Rebar — Rebar is placed, spaced per engineering. Verticals go against the Airform; horizontals go on the outside. Additional plywood frames for doors and windows can be set against the inflated Airform. Remove from inside after concrete sets. One inch of Shotcrete is applied to the exterior of the Airform, allowed to set, then recoated to finish. (Concrete can be hand applied with a trowel.)